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I have created a subset of arrays: 

b = Subsets[Range[10], {5}]
(* Out= {{1, 2, 3, 4, 5}, {1, 2, 3, 4, 6}, {1, 2, 3, 4, 7}, {1, 2, 3, 4, 8},
         {1, 2, 3, 4, 9}, ..., {6, 7, 8, 9, 10}} *)

This command shows the combinations I wish to evaluate with. How can I add the elements of each subset in the list above to get an output like:

{{15}, {16}, {17}, {18}, {19},..., {40}}
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2 Answers 2

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Not sure I follow, but maybe Total[b, {2}]?

If the list of lists form is important: Transpose@{Total[b, {2}]}, or more simply as Artes just posted: List /@ Total[b, {2}]

Subsets returns an unpacked array, and in that case Plus @@@ b is faster. However, by packing the array this method will be an order of magnitude faster than Plus:

Transpose@{Total[Developer`ToPackedArray@b, {2}]}
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  • $\begingroup$ I didn't realize that Plus can ever be faster than Total $\endgroup$
    – Szabolcs
    Commented May 18, 2012 at 7:56
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Use Applyon the first level of the list b (@@@ is a shorthand), i.e. 

Plus @@@ b

Or exactly what you want, then map List over Plus @@@ b, i.e.

List /@ Plus @@@ b
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    $\begingroup$ Aiming for brevity, you could also use: Tr /@ b $\endgroup$
    – Mr.Wizard
    Commented May 17, 2012 at 19:40
  • $\begingroup$ Precisely {#} & /@ Tr /@ b. $\endgroup$
    – Artes
    Commented May 17, 2012 at 22:22
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    $\begingroup$ List is as short as {#}& :-) $\endgroup$
    – Mr.Wizard
    Commented May 18, 2012 at 3:07

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